Reflective mask blank and reflective mask

Abstract

The purpose of the present invention is to provide an EUV photomask blank and an EUV photomask having high resistance to hydrogen radicals, low EUV reflectance, and a high OD value. A reflective mask blank (10) according to the present embodiment comprises at least a substrate (1), a multilayer reflective film (2), a capping layer (3), and a low-reflection part (5). The low-reflection part (5) is formed by alternately laminating a first absorption film (51) and a second absorption film (52). The first absorption film (51) has high hydrogen radical resistance, and the extinction coefficient or refractive index of the first absorption film (51) is different from the extinction coefficient or refractive index of the second absorption film (52). The extinction coefficient of the second absorption film (52) with respect to EUV light is 0.04 or more.

Description

Reflective mask blanks and reflective masks

[0001] The present invention relates to a reflective mask blank and a reflective mask used in the manufacture of semiconductor devices and the like.

[0002] In the semiconductor device manufacturing process, the miniaturization of semiconductor devices has led to an increasing demand for miniaturization of photolithography technology. In photolithography, the minimum development dimension of a transfer pattern is highly dependent on the wavelength of the exposure light source, and the shorter the wavelength, the smaller the minimum resolution dimension. For this reason, in the semiconductor device manufacturing process, the conventional exposure light source using ArF excimer laser light with a wavelength of 193 nm has been replaced with an EUV exposure light source with a wavelength of 13.5 nm.

[0003] Because EUV light has a short wavelength, most materials have high optical absorption. Therefore, EUV photomasks (EUV masks) are reflective masks, unlike conventional transmissive masks (see, for example, Patent Documents 1 and 2). Patent Document 1 discloses a reflective exposure mask used in EUV lithography, in which a multilayer film is formed on a base substrate by periodically stacking two or more material layers, and a mask pattern is formed on the multilayer film by forming a pattern made of a metal film containing nitride or a layered structure of a metal nitride film and a metal film. Patent Document 2 also discloses a reflective EUV mask having a phase control film as an absorber film on the multilayer reflective film, and a layered structure in which high-refractive-index material layers and low-refractive-index material layers are alternately stacked on the phase control film.

[0004] As mentioned above, EUV lithography cannot use refractive optics, which utilize the transmission of light, so the optical components of the exposure machine are mirrors rather than lenses. This poses the problem that the light incident on the EUV photomask and the light reflected from the EUV photomask cannot be designed to be coaxial. Therefore, EUV lithography typically employs a method in which the EUV light is incident on the EUV photomask with its optical axis tilted 6 degrees from the perpendicular direction, and the reflected light reflected at an angle of minus 6 degrees is irradiated onto the semiconductor substrate.

[0005] As described above, in EUV lithography, since the optical axis is tilted, EUV light incident on the EUV photomask casts a shadow of the EUV photomask pattern (absorber layer pattern), which can cause a problem called the "shadowing effect," in which transfer performance is deteriorated. To address this problem, Patent Document 1 discloses a method in which a phase control film and a low-refractive index material layer are used, with an extinction coefficient k for EUV of 0.03 or more, thereby enabling a thinner absorber layer thickness (60 nm or less) than conventional ones, thereby reducing the shadowing effect. Patent Document 2 also discloses a method in which a reflectance of EUV light can be reduced to 2% or less with a thinner absorber layer thickness than conventional ones, by alternately stacking high-refractive index material layers and low-refractive index materials as an absorber film.

[0006] Furthermore, current EUV exposure equipment uses cleaning with hydrogen radicals to prevent contamination inside the chamber. Since photomasks are exposed to a hydrogen radical environment, if the mask's durability against hydrogen radicals is low, its lifespan may be shortened. Therefore, photomasks must be made from compound materials that are highly resistant to hydrogen radicals.

[0007] However, the methods of Patent Documents 1 and 2 do not mention hydrogen radical resistance, and it is not clear whether the photomasks can withstand long-term use.

[0008] Patent No. 6408790 Patent No. 6661724

[0009] As described above, there have been no reflective mask blanks and reflective masks according to the prior art that have low EUV reflectivity (higher absorption) and improved resistance to hydrogen radicals while minimizing the projection effect. Therefore, an object of the present invention is to provide a reflective mask blank (EUV photomask blank) and a reflective mask (EUV photomask) that have high resistance to hydrogen radicals and excellent transferability by minimizing the projection effect. In other words, an object of the present invention is to provide an EUV photomask blank (reflective mask blank) and an EUV photomask (reflective mask) that have high resistance to hydrogen radicals, low EUV reflectivity, and a high OD value.

[0010] A reflective mask blank according to one embodiment of the present invention is a reflective mask blank used in the manufacture of a reflective mask for pattern transfer using extreme ultraviolet light as a light source, and comprises at least a substrate, a multilayer film formed on the substrate, a capping film formed on the multilayer film to protect the multilayer film, and an absorbing film formed on the capping film, wherein the absorbing film is formed by alternately laminating first absorbing films and second absorbing films, the first absorbing film has high hydrogen radical resistance, the extinction coefficient or refractive index of the first absorbing film is different from the extinction coefficient or refractive index of the second absorbing film, and the extinction coefficient of the second absorbing film for EUV light is 0.04 or more.

[0011] A reflective mask according to one aspect of the present invention comprises at least a substrate, a multilayer film formed on the substrate, a capping film formed on the multilayer film to protect the multilayer film, and an absorbing film formed and patterned on the capping film, wherein the absorbing film is formed by alternately laminating first absorbing films and second absorbing films, the first absorbing film has high hydrogen radical resistance, the extinction coefficient or refractive index of the first absorbing film is different from the extinction coefficient or refractive index of the second absorbing film, and the extinction coefficient of the second absorbing film for EUV light is 0.04 or more.

[0012] According to one aspect of the present invention, by alternately stacking, as absorbing films, a first absorbing film having high hydrogen radical resistance and a second absorbing film having an EUV extinction coefficient of 0.04 or more, it is possible to provide an EUV photomask blank (reflective mask blank) and an EUV photomask (reflective mask) that have high resistance to hydrogen radicals and excellent transferability by minimizing the projection effect. More specifically, according to one aspect of the present invention, by alternately stacking, as absorbing films, a first absorbing film having high hydrogen radical resistance and a second absorbing film having an EUV extinction coefficient of 0.04 or more, it is possible to provide an EUV photomask blank (reflective mask blank) and an EUV photomask (reflective mask) that have high resistance to hydrogen radicals, low EUV reflectivity, and a high OD value.

[0013] Fig. 1 is a cross-sectional view schematically showing the configuration of a reflective photomask blank according to an embodiment of the present invention; Fig. 2 is a cross-sectional view schematically showing the configuration of a reflective photomask according to an embodiment of the present invention; Fig. 3 is a graph showing the optical constants of each metal at the wavelength of EUV light; Fig. 4 is a conceptual diagram showing a method for evaluating hydrogen radical resistance according to the present embodiment; Fig. 5 is a cross-sectional view schematically showing a modified example of a reflective photomask according to an embodiment of the present invention;

[0014] An embodiment of the present invention will be described with reference to the drawings. The configurations shown in the drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, and the like differ from the actual configurations. Furthermore, the embodiments shown below are merely examples of configurations that embody the technical concept of the present invention, and the technical concept of the present invention is not limited to the materials, shapes, structures, and the like of the components described below. Various modifications can be made to the technical concept of the present invention within the technical scope defined by the claims.

[0015] (Configuration of Reflective Photomask) The basic configurations of a reflective photomask blank (reflective mask blank) and a reflective photomask (reflective mask) according to an embodiment of the present invention will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a schematic cross-sectional view showing a reflective photomask blank 10 according to an embodiment of the present invention. Fig. 2 is a schematic cross-sectional view showing a reflective photomask 20 according to an embodiment of the present invention. Here, the reflective photomask 20 according to the embodiment of the present invention shown in Fig. 2 is formed by patterning the reflective layer 4 of the reflective photomask blank 10 according to the embodiment of the present invention shown in Fig. 1.

[0016] A reflective photomask blank 10 according to an embodiment of the present invention is a reflective photomask blank used in the manufacture of a reflective photomask for pattern transfer using extreme ultraviolet light as a light source, and includes at least a substrate (low thermal expansion film) 1, a multilayer reflective film (multilayer film) 2 formed on the substrate 1, a capping film (capping layer) 3 formed on the multilayer reflective film 2 to protect the multilayer reflective film 2, and a low-reflection portion (absorption film) 5 formed on the capping film 3. The low-reflection portion 5 is a laminate in which first absorption films 51 and second absorption films 52 are alternately stacked. The first absorption film 51 is a layer formed of a material with high hydrogen radical resistance. The extinction coefficient or refractive index of the first absorption film 51 is different from the extinction coefficient or refractive index of the second absorption film 52. The extinction coefficient of the second absorption film 52 for EUV light is 0.04 or greater.

[0017] The following describes in detail each of the components of the reflective photomask blank 10 and the reflective photomask 20.

[0018] 1 , a reflective photomask blank 10 according to an embodiment of the present invention includes a multilayer reflective film 2 on a substrate 1, and a capping layer 3 on the multilayer reflective film 2. As a result, a reflective layer 4 having the multilayer reflective film 2 and the capping layer 3 is formed on the substrate 1. In addition, a low-reflection portion 5 is provided on the reflective layer 4. The low-reflection portion 5 is a laminate composed of, for example, four or more layers, and is a laminate alternately including, as a first layer, a first absorbing film 51 having high hydrogen radical resistance and, as a second layer, a second absorbing film 52 having an extinction coefficient of 0.04 or more.

[0019] (Substrate) The substrate 1 according to the embodiment of the present invention may be a flat Si substrate, a synthetic quartz substrate, etc. Also, low thermal expansion glass containing titanium may be used, but the present invention is not limited to these as long as the material has a small thermal expansion coefficient.

[0020] (Multilayer Reflective Film) The multilayer reflective film 2 according to the embodiment of the present invention reflects EUV light (extreme ultraviolet light), which is exposure light, and is composed of a multilayer film made of a combination of materials with significantly different refractive indices for EUV light. For example, the multilayer reflective film 2 can be formed by repeatedly stacking layers of a combination of Mo (molybdenum) and Si (silicon) or Mo (molybdenum) and Be (beryllium) in about 40 cycles.

[0021] (Capping Layer) The capping layer (capping film) 3 according to the embodiment of the present invention is formed from a material that is resistant to the dry etching performed when forming the low-reflection portion pattern 5a, and functions as an etching stopper that prevents damage to the multilayer reflective film 2 when forming the low-reflection portion pattern 5a by etching. Here, the capping layer 3 may be unnecessary depending on the material of the multilayer reflective film 2 and the etching conditions. Furthermore, a back surface conductive film 6 can be formed on the surface of the substrate 1 on which the multilayer reflective film 2 is not formed. The back surface conductive film 6 is a film that uses the principle of an electrostatic chuck to fix the reflective photomask 20 when it is placed in an exposure machine.

[0022] (Low-Reflectivity Portion) A low-reflectivity portion pattern 5a is formed by removing a portion of the low-reflectivity portion 5 of the reflective photomask blank 10. In EUV lithography, EUV light is incident at an angle and reflected by the reflective layer 4. However, the low-reflectivity portion pattern 5a obstructs the light path, resulting in a projection effect, which deteriorates the transfer performance onto the wafer. This deterioration in transfer performance can be reduced by reducing the thickness of the low-reflectivity portion 5 (low-reflectivity portion pattern 5a) that absorbs EUV light. The thickness of the low-reflectivity portion 5 (low-reflectivity portion pattern 5a) can be reduced by using a material that is highly absorbent of EUV light for the second absorption film 52, i.e., a material with a high extinction coefficient k at a wavelength of 13.5 nm, and by using a film with a different extinction coefficient or refractive index from that of the second absorption film 52 for the first absorption film 51, and stacking these films alternately.

[0023] In this embodiment, "high extinction coefficient k" means that the extinction coefficient k is 0.04 or greater. Forming the second absorption film 52 using a compound material having an extinction coefficient k of 0.04 or greater reduces the film thickness of the second absorption film 52, thereby enabling the thickness of the low-reflection portion 5 to be reduced. Compound materials having an extinction coefficient k of 0.04 or greater include, for example, the materials shown in FIG. 3 . Compound materials having an extinction coefficient k of 0.04 or greater (second absorption film material group) include, as shown in FIG. 3 , materials containing one or more elements selected from tin, indium, platinum, nickel, tellurium, silver, cobalt, tantalum, antimony, bismuth, osmium, iridium, and rhenium. Note that FIG. 3 also illustrates, as a group of materials having high hydrogen radical resistance (first absorption film material group), materials containing one or more elements selected from tantalum, silicon, titanium, niobium, chromium, hafnium, ruthenium, molybdenum, aluminum, and zirconium.

[0024] By using a group of materials with high hydrogen radical resistance as the material for the first absorption film 51 constituting the low-reflectivity portion 5 of this embodiment, it is possible to increase the hydrogen radical resistance of the entire low-reflectivity portion 5. Note that in this embodiment, the "material with high hydrogen radical resistance" refers to a compound material that undergoes film reduction of 1 nm or less in an excited hydrogen radical environment under conditions set to a distance of 18 mm between electrodes 301 using, for example, the apparatus shown in FIG. 4 , a hydrogen flow rate of 100 sscm, and MWP (Micro Wave Plasma) of 2.45 GHz. Also, the "film (layer) with excellent hydrogen radical resistance" refers to a film (layer) that undergoes film reduction of 1 nm or less in the above-mentioned hydrogen radical environment.

[0025] The first absorption film 51 preferably contains one or more elements selected from tantalum, silicon, titanium, niobium, chromium, hafnium, ruthenium, molybdenum, aluminum, and zirconium. If the first absorption film 51 contains any of the above elements, excellent hydrogen radical resistance can be imparted to the first absorption film 51. Furthermore, it is preferable that the outermost layer of the low reflectivity portion 5 is the first absorption film 51. If the outermost layer of the low reflectivity portion 5 is the first absorption film 51, excellent hydrogen radical resistance can be imparted to the entire low reflectivity portion 5.

[0026] The second absorption film 52 preferably contains one or more elements selected from tin, indium, platinum, nickel, tellurium, silver, cobalt, tantalum, antimony, bismuth, osmium, iridium, and rhenium. If the second absorption film 52 contains any of the above elements, the extinction coefficient k of the second absorption film 52 becomes greater than 0.04, and the projection effect can be reduced.

[0027] Furthermore, if the above-mentioned material having high hydrogen radical resistance is mixed into the second absorption film 52 as well, it is possible to further improve the hydrogen radical resistance, which is more preferable. In this case, there is no particular problem as long as the extinction coefficient k of the entire low-reflectivity portion 5 is 0.04 or more. There is also no particular problem as long as the extinction coefficient k of the second absorption film 52 is 0.04 or more. In this embodiment, the extinction coefficient and refractive index of each absorption film may be adjusted by appropriately adjusting the composition ratio of the materials constituting each absorption film.

[0028] Furthermore, if it is necessary to suppress damage caused by hydrogen radicals on the side surfaces of the low-reflection portion pattern 5a, a passivation (also referred to as "passivation") treatment may be performed. As shown in FIG. 5 , the passivation treatment can form a highly hydrogen radical-resistant passive layer 52a on the pattern side surfaces of the second absorption film 52, thereby further improving the hydrogen radical resistance. For example, the highly hydrogen radical-resistant material constituting the first absorption film 51 may be added to the second absorption film 52, thereby forming an oxide film (passive layer 52a) on the pattern side surfaces of the second absorption film 52. The content of the highly hydrogen radical-resistant material added to the second absorption film 52 is not particularly limited as long as the extinction coefficient k of the second absorption film 52 is 0.04 or greater.

[0029] From the viewpoint of improving resistance, it is preferable that the film thickness of this thin film layer (passive layer 52 a) (specifically, the thickness from the side surface of the pattern) is in the range of 0.5 nm to 8 nm, from the viewpoint of improving transferability, it is even more preferable that the film thickness is in the range of 0.5 nm to 5 nm, and from the viewpoint of achieving both improved resistance and improved transferability, it is even more preferable that the film thickness is in the range of 2 nm to 5 nm.

[0030] The passive layer 52a formed on the pattern side surface of the second absorption film 52 can be formed by a chemical treatment method using, for example, SPM or APM. Other chemicals or gases may also be used as the treatment method. The passive layer 52a may be an oxide film, and there is no problem if the oxide film is formed by the above-mentioned methods or by natural oxidation.

[0031] The thickness of the passive layer 52a may be thicker in the second absorbing film 52 closer to the capping layer 3 and thinner in the second absorbing film 52 closer to the outermost surface of the low-reflectivity portion 5. The thickness of the passive layer 52a may be thin in the second absorbing film 52 closer to the capping layer 3 and thick in the second absorbing film 52 closer to the outermost surface of the low-reflectivity portion 5. The thickness of the passive layer 52a may be adjusted by appropriately adjusting the treatment time and the type of treatment agent.

[0032] To reduce the shadow effect, the mixing ratio of the materials forming the low-reflection portion 5 must be adjusted so that the total film thickness of the low-reflection portion 5 is 47 nm or less, and to maintain a contrast sufficient for pattern transfer, the OD value is 1.5 or greater. The lower limit of the mixing ratio cannot be determined in general because it depends on the optical constants of the materials being mixed. However, to reduce the shadow effect compared to conventional films, it is desirable that the materials forming the second absorption film 52 be compound materials containing at least 50 atomic % or more of non-metallic elements. Furthermore, to transfer fine patterns, it is desirable to have a high contrast between the intensity of light reflected by the reflective layer 4 and the low-reflection portion 5. Therefore, it is more preferable that the OD value of the low-reflection portion 5 is 2.0 or greater.

[0033] Here, we will explain the optical density (OD) value, which is an index representing the contrast in light intensity between the reflective layer 4 and the low-reflection portion 5. When the intensity of reflected light from the reflective layer 4 is Rm and the intensity of reflected light from the low-reflection portion 5 is Ra, the OD value is defined by the following formula (1): OD=-log(Ra / Rm) Formula (1) The larger the OD value, the better the contrast and the higher the transferability. In a reflective photomask, OD>1 is required for pattern transfer, but in order to obtain higher transferability than conventional films, an OD value of 1.5 or more is more preferable.

[0034] In this embodiment, it is desirable that the number of layers of the first absorption film 51 and the second absorption film 52 is 4 or more. If the number of layers is 4 or more, various combinations of materials and film thicknesses that can achieve thinning become possible. Furthermore, if the number of layers is within a range of 4 to 40, a sufficient thinning can be achieved, and if it is within a range of 4 to 16, more combinations of materials and film thicknesses are possible, which is more preferable.

[0035] Furthermore, the refractive index of the constituent material of the first absorbing film 51 is preferably within a range of 0.85 or more and 1 or less. From the viewpoint of the number of combinations of materials, it is more desirable that the refractive index of the constituent material of the first absorbing film 51 is different from that of the constituent material of the second absorbing film 52. The refractive index of the constituent material of the first absorbing film 51 may be larger or smaller than the refractive index of the constituent material of the second absorbing film 52. Of course, the refractive index of the constituent material of the first absorbing film 51 may be the same as the refractive index of the constituent material of the second absorbing film 52.

[0036] Furthermore, from the viewpoint of the number of material combinations, it is more desirable that the extinction coefficient k of the constituent material of the first absorbing film 51 be different from that of the constituent material of the second absorbing film 52. Note that the extinction coefficient k of the constituent material of the first absorbing film 51 may be larger or smaller than the extinction coefficient k of the constituent material of the second absorbing film 52. Of course, the extinction coefficient k of the constituent material of the first absorbing film 51 may be the same as the extinction coefficient k of the constituent material of the second absorbing film 52.

[0037] Furthermore, the thickness of each absorbing film may be 0.1 nm or more. The film thickness of the low-reflectivity portion 5 is not particularly limited as long as the combined film thickness of the first absorbing film 51 and the second absorbing film 52 is such that the total film thickness of each absorbing film is 47 nm or less and the OD value is 1.5 or more. For example, the film thickness of the first absorbing film 51 and the film thickness of the second absorbing film 52 may be the same. Furthermore, the film thickness of the first absorbing film 51 may be thinner than the film thickness of the second absorbing film 52. Furthermore, the film thickness of the first absorbing film 51 may be thicker than the film thickness of the second absorbing film 52. Furthermore, the film thickness of each absorbing film may be gradually thinner or thicker in the direction away from the capping layer 3 (toward the outermost surface of the low-reflectivity portion 5).

[0038] EXAMPLES The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0039] Example 1: A synthetic quartz substrate with low thermal expansion was used as the substrate. A multilayer reflective film was formed on the substrate by stacking 40 layers of a silicon (Si) / molybdenum (Mo) multilayer film. The film thickness of the multilayer reflective film was 280 nm.

[0040] Next, a capping layer was formed on the multilayer reflective film using ruthenium (Ru) to a thickness of 2.5 nm. A second absorbing film was formed on the capping layer using tin oxide (SnO) and tantalum (Ta). The thickness of the absorbing film (single layer) was 11.4 nm. The refractive index n of the thus formed second absorbing film was 0.95, and the extinction coefficient k was 0.050.

[0041] Next, a first absorbing film was formed on the second absorbing film using tantalum oxide (TaO). The thickness of the absorbing film (single layer) was 1.9 nm. The refractive index n of the first absorbing film thus formed was 0.96, and the extinction coefficient k was 0.027.

[0042] Next, the first absorbing film and the second absorbing film were alternately stacked to form an absorbing film with a total number of stacked layers of 6 (a stack consisting of three layers of the first absorbing film and three layers of the second absorbing film). The total film thickness of the entire absorbing film thus formed was 39.9 nm.

[0043] Next, a backside conductive film of chromium nitride (CrN) was formed to a thickness of 100 nm on the side of the substrate where the multilayer reflective film was not formed. In this way, a reflective photomask blank according to Example 1 was produced. A multi-target sputtering device was used to form each film on the substrate. The film thickness of each film was controlled by the sputtering time.

[0044] Next, a positive chemically amplified resist (SEBP9012, manufactured by Shin-Etsu Chemical Co., Ltd.) was spin-coated on the absorbing film to a thickness of 120 nm, and baked at 110° C. for 10 minutes to form a resist film.

[0045] Next, a predetermined pattern was written on the positive chemically amplified resist using an electron beam lithography machine (JBX3030, manufactured by JEOL Ltd.), followed by baking at 110°C for 10 minutes and then spray development (SFG3000, manufactured by Sigma Meltec Co., Ltd.), thereby forming a resist pattern.

[0046] Next, using the resist pattern as an etching mask, each absorber film was patterned by dry etching using a chlorine-based gas to form an absorber film pattern. Next, the remaining resist pattern was peeled off. Thus, an absorber film pattern was formed in which the surface and side surfaces of the absorber film were exposed. In this example, the absorber layer pattern was an L / S (line and space) pattern with a line width of 200 nm. In this way, a reflective photomask according to Example 1 was fabricated. For the absorber film of Example 1, the reflectance Rm of the multilayer reflective film region and the reflectance Ra of the absorber film region were measured using a reflectance measuring device using EUV light. From the measurement results, the OD value, which is a mask characteristic, was calculated. As shown in Table 1, it was found that the EUV reflectance in the absorber film region was 0.70% and the OD value was 1.96.

[0047] Example 2 A reflective photomask blank and a reflective photomask according to Example 2 were produced in the same manner as in Example 1, except that the film thickness of the second absorbing film (single layer) was set to 11.1 nm and the film thickness of the first absorbing film (single layer) formed using silicon oxide (SiO) was set to 2.5 nm. The refractive index n of the first absorbing film was 0.97 and the extinction coefficient k was 0.013. The total film thickness of the entire absorbing film was 40.8 nm. The EUV reflectivity in the absorbing film region was 0.74%, and the OD value was 1.94.

[0048] Example 3 A reflective photomask blank and a reflective photomask according to Example 3 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) was set to 10.9 nm and the thickness of the first absorbing film (single layer) formed using titanium oxide (TiO) was set to 2.5 nm. The refractive index n of the first absorbing film was 0.94 and the extinction coefficient k was 0.022. The total thickness of the entire absorbing film was 40.2 nm. The EUV reflectivity in the absorbing film region was 0.63%, and the OD value was 2.01.

[0049] Example 4 A reflective photomask blank and a reflective photomask according to Example 4 were fabricated in the same manner as in Example 1, except that the film thickness of the second absorbing film (single layer) was set to 11.0 nm and the film thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) was set to 2.4 nm. The refractive index n of the first absorbing film was 0.95 and the extinction coefficient k was 0.010. The total film thickness of the entire absorbing film was 40.2 nm. The EUV reflectivity in the absorbing film region was 0.61%, and the OD value was 2.02.

[0050] Example 5 A reflective photomask blank and a reflective photomask according to Example 5 were fabricated in the same manner as in Example 1, except that the film thickness of the second absorbing film (single layer) was set to 10.8 nm and the film thickness of the first absorbing film (single layer) formed using chromium oxide (CrO) was set to 2.6 nm. The refractive index n of the first absorbing film was 0.93 and the extinction coefficient k was 0.033. The total film thickness of the entire absorbing film was 40.2 nm. The EUV reflectivity in the absorbing film region was 0.67%, and the OD value was 1.99.

[0051] Example 6 A reflective photomask blank and a reflective photomask according to Example 6 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) was set to 11.1 nm and the thickness of the first absorbing film (single layer) formed using hafnium oxide (HfO) was set to 2.2 nm. The refractive index n of the first absorbing film was 0.95 and the extinction coefficient k was 0.034. The total thickness of the entire absorbing film was 39.9 nm. The EUV reflectivity in the absorbing film region was 0.72%, and the OD value was 1.95.

[0052] Example 7 A reflective photomask blank and a reflective photomask according to Example 7 were fabricated in the same manner as in Example 1, except that the film thickness of the second absorbing film (single layer) was set to 10.4 nm and the film thickness of the first absorbing film (single layer) formed using ruthenium (Ru) was set to 2.6 nm. The refractive index n of the first absorbing film was 0.89 and the extinction coefficient k was 0.017. The total film thickness of the entire absorbing film was 39.0 nm. The EUV reflectivity in the absorbing film region was 0.71%, and the OD value was 1.96.

[0053] Example 8 A reflective photomask blank and a reflective photomask according to Example 8 were fabricated in the same manner as in Example 1, except that the film thickness of the second absorbing film (single layer) was set to 11.0 nm and the film thickness of the first absorbing film (single layer) formed using molybdenum (Mo) was set to 2.4 nm. The refractive index n of the first absorbing film was 0.92 and the extinction coefficient k was 0.006. The total film thickness of the entire absorbing film was 40.2 nm. The EUV reflectivity in the absorbing film region was 0.37%, and the OD value was 2.25.

[0054] Example 9 A reflective photomask blank and a reflective photomask according to Example 9 were produced in the same manner as in Example 1, except that the film thickness of the second absorbing film (single layer) was set to 11.3 nm and the film thickness of the first absorbing film (single layer) formed using zirconium (Zr) was set to 2.1 nm. The refractive index n of the first absorbing film was 0.96 and the extinction coefficient k was 0.004. The total film thickness of the entire absorbing film was 40.2 nm. The EUV reflectivity in the absorbing film region was 0.54%, and the OD value was 2.08.

[0055] Example 10 A reflective photomask blank and a reflective photomask according to Example 10 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using indium (In) and tantalum (Ta) was 11.5 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 2.2 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.94, and the extinction coefficient k was 0.058. The total thickness of the entire absorbing film was 41.1 nm. The EUV reflectivity in the absorbing film region was 0.13%, and the OD value was 2.71.

[0056] Example 11 A reflective photomask blank and a reflective photomask according to Example 11 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using nickel (Ni) and tantalum (Ta) was 11.2 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 2.4 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.95, and the extinction coefficient k was 0.053. The total thickness of the entire absorbing film was 40.8 nm. The EUV reflectivity in the absorbing film region was 0.44%, and the OD value was 2.17.

[0057] Example 12 A reflective photomask blank and a reflective photomask according to Example 12 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using tellurium (Te) and tantalum (Ta) was 10.9 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 2.3 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.96, and the extinction coefficient k was 0.057. The total thickness of the entire absorbing film was 39.6 nm. The EUV reflectivity in the absorbing film region was 0.20%, and the OD value was 2.51.

[0058] Example 13 A reflective photomask blank and a reflective photomask according to Example 13 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using silver (Ag) and tantalum (Ta) was 11.4 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 2.6 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.92, and the extinction coefficient k was 0.060. The total thickness of the entire absorbing film was 42.0 nm. The EUV reflectivity in the absorbing film region was 0.06%, and the OD value was 3.05.

[0059] Example 14 A reflective photomask blank and a reflective photomask according to Example 14 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using cobalt (Co) and tantalum (Ta) was 11.1 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 2.4 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.94, and the extinction coefficient k was 0.051. The total thickness of the entire absorbing film was 40.5 nm. The EUV reflectivity in the absorbing film region was 0.55%, and the OD value was 2.07.

[0060] Example 15 A reflective photomask blank and a reflective photomask according to Example 15 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using antimony (Sb) and tantalum (Ta) was 11.1 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 2.5 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.94, and the extinction coefficient k was 0.053. The total thickness of the entire absorbing film was 40.8 nm. The EUV reflectivity in the absorbing film region was 0.41%, and the OD value was 2.20.

[0061] Example 16 A reflective photomask blank and a reflective photomask according to Example 16 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using bismuth (Bi) and tantalum (Ta) was 11.1 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 2.5 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.94, and the extinction coefficient k was 0.049. The total thickness of the entire absorbing film was 40.8 nm. The EUV reflectivity in the absorbing film region was 0.70%, and the OD value was 1.97.

[0062] Example 17 A reflective photomask blank and a reflective photomask according to Example 17 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using iridium (Ir) and tantalum (Ta) was 11.8 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 2.0 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.93, and the extinction coefficient k was 0.043. The total thickness of the entire absorbing film was 41.4 nm. The EUV reflectivity in the absorbing film region was 1.13%, and the OD value was 1.76.

[0063] Example 18 A reflective photomask blank and a reflective photomask according to Example 18 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using rhenium (Re) and tantalum (Ta) was 11.7 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 2.0 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.93, and the extinction coefficient k was 0.040. The total thickness of the entire absorbing film was 41.1 nm. The EUV reflectivity in the absorbing film region was 1.57%, and the OD value was 1.61.

[0064] Example 19 A reflective photomask blank and a reflective photomask according to Example 19 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using platinum (Pt) and tantalum (Ta) was 11.9 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 2.1 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.92, and the extinction coefficient k was 0.050. The total thickness of the entire absorbing film was 42.0 nm. The EUV reflectivity in the absorbing film region was 0.38%, and the OD value was 2.24.

[0065] Example 20 A reflective photomask blank and a reflective photomask according to Example 20 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using osmium (Os) and tantalum (Ta) was 11.8 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 2.0 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.93, and the extinction coefficient k was 0.042. The total thickness of the entire absorbing film was 41.4 nm. The EUV reflectivity in the absorbing film region was 1.19%, and the OD value was 1.73.

[0066] Example 21 A reflective photomask blank and a reflective photomask according to Example 21 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using tin oxide (SnO) and tantalum (Ta) was 3.4 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 3.5 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.95, and the extinction coefficient k was 0.050. The total number of layers of the first absorbing film and the second absorbing film was 14, and the total thickness of the entire absorbing film was 48.3 nm. The EUV reflectivity in the absorbing film region was 0.23%, and the OD value was 2.45.

[0067] Example 22 A reflective photomask blank and a reflective photomask according to Example 22 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using tin oxide (SnO) and tantalum (Ta) was 15.8 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 4.3 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.95, and the extinction coefficient k was 0.050. The total number of layers of the first absorbing film and the second absorbing film was 4, and the total thickness of the entire absorbing film was 40.2 nm. The EUV reflectivity in the absorbing film region was 0.51%, and the OD value was 2.11.

[0068] Example 23 A reflective photomask blank and a reflective photomask according to Example 23 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using tin oxide (SnO) and tantalum (Ta) was 9.2 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 2.5 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.95, and the extinction coefficient k was 0.050. The total number of layers of the first absorbing film and the second absorbing film was 8, and the total thickness of the entire absorbing film was 46.8 nm. The EUV reflectivity in the absorbing film region was 0.26%, and the OD value was 2.39.

[0069] Example 24 A reflective photomask blank and a reflective photomask according to Example 24 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using tin oxide (SnO) and tantalum (Ta) was 4.4 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 1.4 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.95, and the extinction coefficient k was 0.050. The total number of layers of the first absorbing film and the second absorbing film was 16, and the total thickness of the entire absorbing film was 40.2 nm. The EUV reflectivity in the absorbing film region was 0.25%, and the OD value was 2.41.

[0070] Example 25 A reflective photomask blank and a reflective photomask according to Example 25 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using tin oxide (SnO) and tantalum (Ta) was 13.9 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 1.7 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.95, and the extinction coefficient k was 0.050. The total thickness of the entire absorbing film was 46.8 nm. The EUV reflectivity in the absorbing film region was 0.22%, and the OD value was 2.47.

[0071] Example 26 A reflective photomask blank and a reflective photomask according to Example 26 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using tin oxide (SnO) and tantalum (Ta) was 4.4 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 2.2 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.95, and the extinction coefficient k was 0.050. The total number of layers of the first absorbing film and the second absorbing film was 12, and the total thickness of the entire absorbing film was 33.0 nm. The EUV reflectivity in the absorbing film region was 1.62%, and the OD value was 1.60.

[0072] Example 27 A reflective photomask blank and a reflective photomask according to Example 27 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using lead (Pb) and tungsten (W) was 11.8 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 2.0 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.93, and the extinction coefficient k was 0.042. The total thickness of the entire absorbing film was 41.4 nm. The EUV reflectivity in the absorbing film region was 1.19%, and the OD value was 1.73.

[0073] Example 28 A reflective photomask blank and a reflective photomask according to Example 28 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using tin oxide (SnO) and tantalum (Ta) was 36.9 nm, and the thickness of the first absorbing film (single layer) formed using ruthenium (Ru) and silicon (Si) was 10.3 nm. The refractive index n of the first absorbing film was 0.90, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.95, and the extinction coefficient k was 0.050. The total number of layers of the first absorbing film and the second absorbing film was 2, and the total thickness of the entire absorbing film was 47.2 nm. The EUV reflectivity in the absorbing film region was 0.24%, and the OD value was 2.43.

[0074] Example 29 A reflective photomask blank and a reflective photomask according to Example 29 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using tin oxide (SnO) and tantalum (Ta) was 4.0 nm, and the thickness of the first absorbing film (single layer) formed using ruthenium (Ru) was 3.9 nm. The refractive index n of the first absorbing film was 0.89, and the extinction coefficient k was 0.017. The refractive index n of the second absorbing film was 0.95, and the extinction coefficient k was 0.050. The total number of layers of the first absorbing film and the second absorbing film was 10, and the total thickness of the entire absorbing film was 39.5 nm. The EUV reflectivity in the absorbing film region was 0.36%, and the OD value was 2.25. In this example, the first absorbing film was formed on the capping layer, and the second absorbing film was formed on the first absorbing film, i.e., the absorbing films were formed so that the second absorbing film was the outermost layer.

[0075] Example 30 A reflective photomask blank and a reflective photomask according to Example 30 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using tin oxide (SnO) and tantalum (Ta) was 16.9 nm, and the thickness of the first absorbing film (single layer) formed using aluminum (Al) and silicon (Si) was 5.5 nm. The refractive index n of the first absorbing film was 1.00, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.95, and the extinction coefficient k was 0.050. The total number of layers of the first absorbing film and the second absorbing film was 4, and the total thickness of the entire absorbing film was 44.8 nm. The EUV reflectivity in the absorbing film region was 0.75%, and the OD value was 1.94.

[0076] Example 31 A reflective photomask blank and a reflective photomask according to Example 31 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using tin oxide (SnO) and tantalum (Ta) was 10.8 nm, and the thickness of the first absorbing film (single layer) formed using tungsten (W) was 2.6 nm. The refractive index n of the first absorbing film was 0.93, and the extinction coefficient k was 0.033. The refractive index n of the second absorbing film was 0.95, and the extinction coefficient k was 0.050. The total thickness of the entire absorbing film was 40.2 nm. The EUV reflectivity in the absorbing film region was 0.67%, and the OD value was 1.99. The tungsten (W) used for the first absorbing film is a material with hydrogen radical resistance.

[0077] Comparative Example 1 A reflective photomask blank and a reflective photomask according to Comparative Example 1 were produced in the same manner as in Example 1, except that the second absorbing film was not provided and the film thickness of the first absorbing film (single layer) formed using tin oxide (SnO) was set to 32.4 nm. The refractive index n of the first absorbing film was 0.93 and the extinction coefficient k was 0.070. The total film thickness of the entire absorbing film was 32.4 nm. The EUV reflectivity in the absorbing film region was 0.20%, and the OD value was 2.51.

[0078] Comparative Example 2 A reflective photomask blank and a reflective photomask according to Comparative Example 2 were fabricated in the same manner as in Example 1, except that the thickness of the second absorbing film (single layer) formed using tin oxide (SnO) and zirconium (Zr) was 18.5 nm, and the thickness of the first absorbing film (single layer) formed using niobium oxide (NbO) and silicon (Si) was 1.6 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.015. The refractive index n of the second absorbing film was 0.95, and the extinction coefficient k was 0.030. The total number of layers of the first absorbing film and the second absorbing film was 4, and the total thickness of the entire absorbing film was 40.2 nm. The EUV reflectivity was 5.19%, and the OD value was 1.10.

[0079] Reference Example The reflective photomask blank and reflective photomask according to the Reference Example are an existing tantalum (Ta) mask blank and an existing tantalum (Ta) mask according to the prior art. The reflective photomask blank and reflective photomask according to the Reference Example were fabricated in the same manner as in Example 1, except that the second absorbing film was not provided, and the film thickness of the first absorbing film (single layer) formed using tantalum nitride (TaN) and tantalum oxide (TaO) was set to 60 nm. The refractive index n of the first absorbing film was 0.95, and the extinction coefficient k was 0.030. The total film thickness of the entire absorbing film was 60.0 nm. The EUV reflectivity in the absorbing film region was 1.83%, and the OD value was 1.54.

[0080] <Evaluation> The reflective photomasks obtained in Examples 1 to 31, Comparative Examples 1 and 2, and Reference Example described above were evaluated for EUV reflectance, OD value, and hydrogen radical resistance by the following methods.

[0081] [EUV Reflectance] In this example, if the measured EUV reflectance was 1.80% or less, the mask was deemed to pass because it had better performance than the existing tantalum (Ta) mask.

[0082] [OD Value] In this example, if the measured OD value was 1.5 or more, there was no problem in use and it was therefore judged to be acceptable.

[0083] [Hydrogen Radical Resistance] Using a 2.45 GHz MWP (Microwave Plasma), hydrogen was excited at a flow rate of 100 sscm, and the prepared reflective photomask was placed on one of the electrodes with an inter-electrode distance of 18 mm. The change in thickness of the absorbing film after hydrogen radical treatment was confirmed using an atomic force microscope (AFM) and evaluated using the following three levels: ◎, ○, and ×. The measurement was performed using an L / S pattern with a line width of 200 nm. In this example, "◎" and "○" were considered to be acceptable.

[0084] <Evaluation criteria> ⊚: No change in film thickness was observed due to hydrogen radicals ◯: A slight change in film thickness was observed due to hydrogen radicals ×: A change in film thickness was observed due to hydrogen radicals The above evaluation results are shown in Table 1.

[0085]

[0086] As shown in Table 1, from the evaluation results of Examples 1 to 31, Comparative Examples 1 and 2, and Reference Example, a reflective photomask blank and a reflective photomask having a configuration in which first absorbing films and second absorbing films are alternately laminated, the first absorbing film is a film with excellent hydrogen radical resistance, the extinction coefficient k or refractive index n of the first absorbing film is different from the extinction coefficient k or refractive index n of the second absorbing film, and the extinction coefficient k of the second absorbing film is 0.04 or higher can provide a reflective photomask blank and a reflective photomask having high resistance to hydrogen radicals, low EUV reflectivity, and a high OD value.

[0087] The reflective photomask blank and reflective photomask according to the present invention are not limited to the above-described embodiments and examples, and various modifications are possible within the scope that does not impair the features of the invention.

[0088] 1: Substrate (low thermal expansion film) 2: Multilayer reflective film 3: Capping layer 4: Reflective layer 5: Low-reflection portion (absorption film) 5a: Low-reflection portion pattern 51: First absorption film 52: Second absorption film 52a: Passivation layer 6: Back surface conductive film 10: Reflective photomask blank (reflective mask blank) 20: Reflective photomask (reflective mask) 300: Chamber 301: Electrode 302: Sample

Claims

1. A reflective mask blank used in the manufacture of a reflective mask for pattern transfer using extreme ultraviolet light as a light source, comprising at least a substrate, a multilayer film formed on the substrate, a capping film formed on the multilayer film to protect the multilayer film, and an absorbing film formed on the capping film, wherein the absorbing film is an alternating stack of a first absorbing film and a second absorbing film, the first absorbing film has high hydrogen radical resistance, the extinction coefficient or refractive index of the first absorbing film is different from the extinction coefficient or refractive index of the second absorbing film, and the extinction coefficient of the second absorbing film for EUV light is 0.04 or more.

2. The reflective mask blank according to claim 1, characterized in that the first absorbing film contains one or more elements selected from the group consisting of tantalum, silicon, titanium, niobium, chromium, hafnium, ruthenium, molybdenum, aluminum and zirconium.

3. The reflective mask blank according to claim 1, characterized in that the second absorbing film contains one or more elements selected from tin, indium, platinum, nickel, tellurium, silver, cobalt, tantalum, antimony, bismuth, osmium, iridium, and rhenium.

4. The reflective mask blank according to claim 1, characterized in that the total thickness of the absorbing film is 47 nm or less.

5. The reflective mask blank according to claim 1, characterized in that the number of layers of the first absorbing film and the second absorbing film is four or more.

6. A reflective mask blank according to claim 1, wherein the outermost layer of said absorbing film is said first absorbing film.

7. The reflective mask blank according to claim 1, wherein an OD (Optical Density) value calculated from the absorbing film and the multilayer film is 1.5 or more.

8. A reflective mask comprising at least a substrate, a multilayer film formed on the substrate, a capping film formed on the multilayer film to protect the multilayer film, and an absorbing film formed on the capping film and patterned, wherein the absorbing film is an alternating stack of a first absorbing film and a second absorbing film, the first absorbing film has high resistance to hydrogen radicals, the extinction coefficient or refractive index of the first absorbing film is different from the extinction coefficient or refractive index of the second absorbing film, and the extinction coefficient of the second absorbing film for EUV light is 0.04 or more.

9. The reflective mask according to claim 8, wherein the first absorbing film contains one or more elements selected from the group consisting of tantalum, silicon, titanium, niobium, chromium, hafnium, ruthenium, molybdenum, aluminum, and zirconium.

10. The reflective mask according to claim 8, wherein the second absorbing film contains one or more elements selected from the group consisting of tin, indium, platinum, nickel, tellurium, silver, cobalt, tantalum, antimony, bismuth, osmium, iridium, and rhenium.

11. The reflective mask according to claim 8, wherein the total thickness of said absorbing film is 47 nm or less.

12. The reflective mask according to claim 8, wherein the number of layers of said first absorbing film and said second absorbing film is four or more.

13. The reflective mask according to claim 8, wherein the outermost layer of said absorbing film is said first absorbing film.

14. The reflective mask according to claim 8, wherein an OD (Optical Density) value calculated from said absorbing film and said multilayer film is 1.5 or more.

15. The reflective mask according to claim 8, wherein an oxide film having high resistance to hydrogen radicals is formed on the side surface of the patterned second absorbing film.

Images